1. Field of the Invention
The invention relates to a sheet-fed scanner capable of switching backgrounds, and more particularly to a sheet-fed scanner capable of scanning a plurality of sections of a background component having different reflectivities as different backgrounds.
2. Description of the Related Art
In a conventional sheet-fed scanner or a flatbed scanner equipped with a scanning module and an automatic document feeder, the scan background cannot be switched because the background for the scanning module is stationary.
The main object of changing the scan background is to find a leading edge, a side edge and a trailing edge of a sheet. The edge-finding procedure enables the scanner to correct the skewness of the sheet, to start and end the image acquiring procedure at proper time instants, and to determine the scanning width. The typical document is white, so the background should be the dark background to facilitate the edge-finding procedure. However, some special documents (e.g., highlighted documents) are in a dark color, so the background should be in white to facilitate the edge-finding procedure. In a color scan mode, the background for the color document may also depend on the color of the document.
In addition, the color of the background may be configured such that the holes of the punched documents, including black-and-white and color documents, cannot affect the scan result. Furthermore, when the scanner scans a thin document, the background color also tends to affect the scan result. In this case, the background color is preferably close to the background color of the document in order to prevent the scan result from being affected. Consequently, the sheet-fed scanner capable of switching backgrounds can enable various image processing functions to be achieved.
Hence, it is an important object of the invention to provide a sheet-fed scanner capable of switching backgrounds such that background of different colors can be selected.